#include<stdio.h>
#include<math.h>
#define PI 3.14
int main(int argc,char *argv[])
{
	float r=0.0f;
	float area = 0.0f;
    scanf("%f", &r);
	area = PI*r*r;
    printf("area = %.2f\n",area);
    return 0;
}

